For me, the link shows a picture-in-picture recording, with the "big" picture being the slides and the small picture being the speaker, so I would consider this to be OK. But I noticed when watching some video on Android that at least one player there did display two streams side-by-side and cut off the left and right margins in a weird way that cut all slides in half, and the speaker almost. So this may or may not depend on the player. Maybe switching to the QT stream or the Flash works better for you than using the HTML5 player.